Some memory systems use a cipher key to encrypt data before it is stored in memory and to decrypt encrypted data after it is read from memory. Some such memory system have their memory organized into separate virtual drives (or “bands”), each with its own secret encryption key. The Trusted Computing Group (TCG) is an organization that provides specifications on how memory can be organized into separate bands. In some situations, it is desired to erase all of the data stored in a band. To do so, the memory system can write 0s to the entire band. However, since a band can be many megabytes in size, doing so may be a very time-consuming process that can result in undesirable user delay. To avoid this delay and provide a “fast erase” operation, instead of erasing the data, the memory system can simply change the secret encryption key assigned to the band. By changing the cipher key assigned to the band, any read from a band will not return valid data because valid data is rendered only when using the same encryption key that was used to initially encrypt the data. That is, even though the encrypted data is still stored in the band, it can never be properly decrypted once the cipher key has been changed. Since the encrypted data can never be read properly, it can be effectively considered “erased.”